
using System;

namespace TextMining.TextTools
{
    class Stemmer {
        private char[] b;
        private int i,     /* offset into b */
                    i_end, /* offset to end of stemmed word */
                    j, k;
        private static int INC = 50;
        /* unit of size whereby b is increased */
		
        public Stemmer() {
            b = new char[INC];
            i = 0;
            i_end = 0;
        }

        public static string DoPorterStemming(string word)
        {
            var s = new Stemmer();
            s.add(word.ToCharArray(), word.Length);
            s.stem();
            return s.ToString();
        }

        /**
		 * Add a character to the word being stemmed.  When you are finished
		 * adding characters, you can call stem(void) to stem the word.
		 */

        public void add(char ch) {
            if (i == b.Length) {
                char[] new_b = new char[i+INC];
                for (int c = 0; c < i; c++)
                    new_b[c] = b[c];
                b = new_b;
            }
            b[i++] = ch;
        }


        /** Adds wLen characters to the word being stemmed contained in a portion
		 * of a char[] array. This is like repeated calls of add(char ch), but
		 * faster.
		 */

        public void add(char[] w, int wLen) {
            if (i+wLen >= b.Length) {
                char[] new_b = new char[i+wLen+INC];
                for (int c = 0; c < i; c++)
                    new_b[c] = b[c];
                b = new_b;
            }
            for (int c = 0; c < wLen; c++)
                b[i++] = w[c];
        }

        /**
		 * After a word has been stemmed, it can be retrieved by toString(),
		 * or a reference to the internal buffer can be retrieved by getResultBuffer
		 * and getResultLength (which is generally more efficient.)
		 */
        public override string ToString() {
            return new String(b,0,i_end);
        }

        /**
		 * Returns the length of the word resulting from the stemming process.
		 */
        public int getResultLength() {
            return i_end;
        }

        /**
		 * Returns a reference to a character buffer containing the results of
		 * the stemming process.  You also need to consult getResultLength()
		 * to determine the length of the result.
		 */
        public char[] getResultBuffer() {
            return b;
        }

        /* cons(i) is true <=> b[i] is a consonant. */
        private bool cons(int i) {
            switch (b[i]) {
                case 'a': case 'e': case 'i': case 'o': case 'u': return false;
                case 'y': return (i==0) ? true : !cons(i-1);
                default: return true;
            }
        }

        /* m() measures the number of consonant sequences between 0 and j. if c is
		   a consonant sequence and v a vowel sequence, and <..> indicates arbitrary
		   presence,

			  <c><v>       gives 0
			  <c>vc<v>     gives 1
			  <c>vcvc<v>   gives 2
			  <c>vcvcvc<v> gives 3
			  ....
		*/
        private int m() {
            int n = 0;
            int i = 0;
            while(true) {
                if (i > j) return n;
                if (! cons(i)) break; i++;
            }
            i++;
            while(true) {
                while(true) {
                    if (i > j) return n;
                    if (cons(i)) break;
                    i++;
                }
                i++;
                n++;
                while(true) {
                    if (i > j) return n;
                    if (! cons(i)) break;
                    i++;
                }
                i++;
            }
        }

        /* vowelinstem() is true <=> 0,...j contains a vowel */
        private bool vowelinstem() {
            int i;
            for (i = 0; i <= j; i++)
                if (! cons(i))
                    return true;
            return false;
        }

        /* doublec(j) is true <=> j,(j-1) contain a double consonant. */
        private bool doublec(int j) {
            if (j < 1)
                return false;
            if (b[j] != b[j-1])
                return false;
            return cons(j);
        }

        /* cvc(i) is true <=> i-2,i-1,i has the form consonant - vowel - consonant
		   and also if the second c is not w,x or y. this is used when trying to
		   restore an e at the end of a short word. e.g.

			  cav(e), lov(e), hop(e), crim(e), but
			  snow, box, tray.

		*/
        private bool cvc(int i) {
            if (i < 2 || !cons(i) || cons(i-1) || !cons(i-2))
                return false;
            int ch = b[i];
            if (ch == 'w' || ch == 'x' || ch == 'y')
                return false;
            return true;
        }

        private bool ends(String s) {
            int l = s.Length;
            int o = k-l+1;
            if (o < 0)
                return false;
            char[] sc = s.ToCharArray();
            for (int i = 0; i < l; i++)
                if (b[o+i] != sc[i])
                    return false;
            j = k-l;
            return true;
        }

        /* setto(s) sets (j+1),...k to the characters in the string s, readjusting
		   k. */
        private void setto(String s) {
            int l = s.Length;
            int o = j+1;
            char[] sc = s.ToCharArray();
            for (int i = 0; i < l; i++)
                b[o+i] = sc[i];
            k = j+l;
        }

        /* r(s) is used further down. */
        private void r(String s) {
            if (m() > 0)
                setto(s);
        }

        /* step1() gets rid of plurals and -ed or -ing. e.g.
			   caresses  ->  caress
			   ponies    ->  poni
			   ties      ->  ti
			   caress    ->  caress
			   cats      ->  cat

			   feed      ->  feed
			   agreed    ->  agree
			   disabled  ->  disable

			   matting   ->  mat
			   mating    ->  mate
			   meeting   ->  meet
			   milling   ->  mill
			   messing   ->  mess

			   meetings  ->  meet

		*/

        private void step1() {
            if (b[k] == 's') {
                if (ends("sses"))
                    k -= 2;
                else if (ends("ies"))
                    setto("i");
                else if (b[k-1] != 's')
                    k--;
            }
            if (ends("eed")) {
                if (m() > 0)
                    k--;
            } else if ((ends("ed") || ends("ing")) && vowelinstem()) {
                k = j;
                if (ends("at"))
                    setto("ate");
                else if (ends("bl"))
                    setto("ble");
                else if (ends("iz"))
                    setto("ize");
                else if (doublec(k)) {
                    k--;
                    int ch = b[k];
                    if (ch == 'l' || ch == 's' || ch == 'z')
                        k++;
                }
                else if (m() == 1 && cvc(k)) setto("e");
            }
        }

        /* step2() turns terminal y to i when there is another vowel in the stem. */
        private void step2() {
            if (ends("y") && vowelinstem())
                b[k] = 'i';
        }

        /* step3() maps double suffices to single ones. so -ization ( = -ize plus
		   -ation) maps to -ize etc. note that the string before the suffix must give
		   m() > 0. */
        private void step3() {
            if (k == 0)
                return;
			
            /* For Bug 1 */
            switch (b[k-1]) {
                case 'a':
                    if (ends("ational")) { r("ate"); break; }
                    if (ends("tional")) { r("tion"); break; }
                    break;
                case 'c':
                    if (ends("enci")) { r("ence"); break; }
                    if (ends("anci")) { r("ance"); break; }
                    break;
                case 'e':
                    if (ends("izer")) { r("ize"); break; }
                    break;
                case 'l':
                    if (ends("bli")) { r("ble"); break; }
                    if (ends("alli")) { r("al"); break; }
                    if (ends("entli")) { r("ent"); break; }
                    if (ends("eli")) { r("e"); break; }
                    if (ends("ousli")) { r("ous"); break; }
                    break;
                case 'o':
                    if (ends("ization")) { r("ize"); break; }
                    if (ends("ation")) { r("ate"); break; }
                    if (ends("ator")) { r("ate"); break; }
                    break;
                case 's':
                    if (ends("alism")) { r("al"); break; }
                    if (ends("iveness")) { r("ive"); break; }
                    if (ends("fulness")) { r("ful"); break; }
                    if (ends("ousness")) { r("ous"); break; }
                    break;
                case 't':
                    if (ends("aliti")) { r("al"); break; }
                    if (ends("iviti")) { r("ive"); break; }
                    if (ends("biliti")) { r("ble"); break; }
                    break;
                case 'g':
                    if (ends("logi")) { r("log"); break; }
                    break;
                default :
                    break;
            }
        }

        /* step4() deals with -ic-, -full, -ness etc. similar strategy to step3. */
        private void step4() {
            switch (b[k]) {
                case 'e':
                    if (ends("icate")) { r("ic"); break; }
                    if (ends("ative")) { r(""); break; }
                    if (ends("alize")) { r("al"); break; }
                    break;
                case 'i':
                    if (ends("iciti")) { r("ic"); break; }
                    break;
                case 'l':
                    if (ends("ical")) { r("ic"); break; }
                    if (ends("ful")) { r(""); break; }
                    break;
                case 's':
                    if (ends("ness")) { r(""); break; }
                    break;
            }
        }

        /* step5() takes off -ant, -ence etc., in context <c>vcvc<v>. */
        private void step5() {
            if (k == 0)
                return;

            /* for Bug 1 */
            switch ( b[k-1] ) {
                case 'a':
                    if (ends("al")) break; return;
                case 'c':
                    if (ends("ance")) break;
                    if (ends("ence")) break; return;
                case 'e':
                    if (ends("er")) break; return;
                case 'i':
                    if (ends("ic")) break; return;
                case 'l':
                    if (ends("able")) break;
                    if (ends("ible")) break; return;
                case 'n':
                    if (ends("ant")) break;
                    if (ends("ement")) break;
                    if (ends("ment")) break;
                    /* element etc. not stripped before the m */
                    if (ends("ent")) break; return;
                case 'o':
                    if (ends("ion") && j >= 0 && (b[j] == 's' || b[j] == 't')) break;
                    /* j >= 0 fixes Bug 2 */
                    if (ends("ou")) break; return;
                    /* takes care of -ous */
                case 's':
                    if (ends("ism")) break; return;
                case 't':
                    if (ends("ate")) break;
                    if (ends("iti")) break; return;
                case 'u':
                    if (ends("ous")) break; return;
                case 'v':
                    if (ends("ive")) break; return;
                case 'z':
                    if (ends("ize")) break; return;
                default:
                    return;
            }
            if (m() > 1)
                k = j;
        }

        /* step6() removes a final -e if m() > 1. */
        private void step6() {
            j = k;
			
            if (b[k] == 'e') {
                int a = m();
                if (a > 1 || a == 1 && !cvc(k-1))
                    k--;
            }
            if (b[k] == 'l' && doublec(k) && m() > 1)
                k--;
        }

        /** Stem the word placed into the Stemmer buffer through calls to add().
		 * Returns true if the stemming process resulted in a word different
		 * from the input.  You can retrieve the result with
		 * getResultLength()/getResultBuffer() or toString().
		 */
        public void stem() {
            k = i - 1;
            if (k > 1) {
                step1();
                step2();
                step3();
                step4();
                step5();
                step6();
            }
            i_end = k+1;
            i = 0;
        }

        /** Test program for demonstrating the Stemmer.  It reads text from a
		 * a list of files, stems each word, and writes the result to standard
		 * output. Note that the word stemmed is expected to be in lower case:
		 * forcing lower case must be done outside the Stemmer class.
		 * Usage: Stemmer file-name file-name ...
		 */
        
        /*
		public static void Main( String[] args ) {
			if ( args.Length == 0 ) {
				Console.WriteLine( "Usage:  Stemmer <input file>" );
				return;
			}
			char[] w = new char[501];
			Stemmer s = new Stemmer();
			for (int i = 0; i < args.Length; i++)
				try {
					FileStream _in = new FileStream( args[i], FileMode.Open, FileAccess.Read );
					try {
						while(true) {
							int ch = _in.ReadByte();
							if ( Char.IsLetter((char) ch)) {
								int j = 0;
								while(true) {
									ch = Char.ToLower((char) ch);
									w[j] = (char) ch;
									if (j < 500)
										j++;
									ch = _in.ReadByte();
									if (!Char.IsLetter((char) ch)) {
										// to test add(char ch) 
										for (int c = 0; c < j; c++)
											s.add(w[c]);
										// or, to test add(char[] w, int j) 
										// s.add(w, j); 
										s.stem();
								
										String u;

										// and now, to test toString() : 
										u = s.ToString();

										// to test getResultBuffer(), getResultLength() : 
										// u = new String(s.getResultBuffer(), 0, s.getResultLength()); 

										Console.Write(u);
										break;
									}
								}
							}
							if (ch < 0)
								break;
							Console.Write((char)ch);
						}
					} catch (IOException ) {
						Console.WriteLine("error reading " + args[i]);
						break;
					}
				} catch (FileNotFoundException ) {
					Console.WriteLine("file " + args[i] + " not found");
					break;
				}
		}
        */
            
    }
}